1. Field of the Invention
This invention relates to a heat storage device for storing a heat transfer medium such as water for air conditioning.
2. Description of the Prior Art
Recently, heat storage apparatus provided with a heat storage tank for storing a heat transfer medium such as warm water for room heating or cold water for room cooling, have been extensively used. The heat storage tank is effective for storing heat transfer medium for air conditioning and leveling power load. However, in the heat storage tank the heat transfer medium is diffused, so that it is difficult to form a constant temperature layer and high heat loss is liable.
More particularly, in prior art heat storage devices such as shown in FIG. 1, water 2 which serves as heat transfer medium is stored in heat storage tank 1, and cold water approximately at 9.degree. C. led from a primary heat exchanger through a duct line 3 to be discharged in a bottom portion of a tank. When desired, cold water at about 9.degree. C. is taken out from the bottom portion of the tank through the duct line 3 for heat exchange in a secondary heat exchanger for room cooling. In such a heat storage tank, however, water flows obliquely so that it is difficult to form a constant temperature layer. Further, a large dead water zone of water is formed which can hardly flow. Therefore, the cold water storage efficiency is low, and cold water cannot be sufficiently taken out when required by the secondary heat exchanger.
Further, in order to minimize loss due to diffusion, it is necessary to increase the ratio of the depth to the width of the tank. However, even if the depth-to-width ratio is increased, diffusion of heat transfer medium occurs, depending upon the flow of heat transfer medium into and out of the tank. Therefore, the constant temperature layer is liable to be disturbed so that it is not so easy to maintain the temperature of this layer.